2013-09-04

Run levels in linux

Pranaam to all bhai ji _/\_
in this post , we will discuss about run level in linux .
Runlevel is termed as state of the system , means a particular run level will decide how our linux os will work and its behavior . Every run level has its own functionality .
command to check our current run level is  runlevel . when we run command runlevel , we will get output like this
previous_runlevel  current_runlevel
here previous_runlevel represent system orevious runlevel in which we were and current_runlevel for our present runlevel in which our system is working .


if we started our system and system booted in graphical mode, out put of runlevel command will be
n   3
n for neutral and 3 for command line interface . lets discuss about them ;)

we have 7 run level in linux. From 0 to 6
To change run level from one to another we use this command
init  run_level
for example , we are changing system state from our current run level to runlevel 3, command will be init 3

here is the list of runlevels and behavior of system at that runlevel :-

init 0 It is halted mode or you can say when system is off

init1 Its single user mode and specially for administrative tasks . this runlevel have command line
            environment and dont have networking enabled .

init 2 This is multi user command line mode without networking

init 3 Run level 3 is multi user command line mode with networking enabled

init 4 This run level doesnt use by user and for research purpose .

init 5 Run level 5 aka graphical user interface ke mummy  \ ^_^ / . This is the linux graphical user
             interface runlevel . we get graphical environment for performing our task. if we start our machine
             and get a graphical interface for login , it means our system is set to launch runlevel 5 when it starts.

init 6 and this one is also known as re starter for system i.e if we command our system to  change
             runlevel to 6, it means our system gonna reboot.

 if you want that our system should  prompt us with command line interface in runlevel 3 instead of    
  graphical  login panel , we need to edit /etc/inittab file in which our system default runlevel is defined.
open /etc/inittab file either with vi editor(how to use vi editor http://www.mannulinux.org/2013/08/vi-file-editor-in-linux.html) or in nano editor


here , my system default runlevel is 5 i.e when i will boot up my system, i will be prompted with graphical user interface .
But i want to change it to command line interface with networking enabled mode which is runlevel  3. We need to replace number 5 with number 3 and our default runlevel will set to 3.
like this ;)


save it and reboot system. and we will be dropped at command line login panel every time by linux os ;)


ok . if you dont want to work in command line(which is best one from view point of  extra load on system due graphical interface) , you can switch to graphical  user interface by issuing command  init 5
you will be redirected to Graphical user interface


sooo, this was a short description about linux runlevel :)
Hope this will help you .
now i am shutting down i.e  init 0  :D

Thank you
Greetz To:- Guru ji zero cool, Team IndiShell leads and Hardeep bhai <3
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